Normally, when the calculator is in degree mode, the trigonometric functions only return values calculated in degrees. With the r symbol you can have the angle evaluated as if in radian mode because it converts the angle into degrees.
One full rotation around a circle is 2π radians, which is equal to 360°. To convert an angle in radians to degrees you multiply by 180/π, and to convert from degrees to radians multiply by π/180.
In degree mode:
sin(π) \\sine of Pi degrees .0548036651 sin(π^^r) 0
In radian mode:
sin(π) 0 sin(π^^r) 0 \\There's no difference when in radians
When you only call the trig function once in a program and want it calculated in radians, instead of changing the mode you can just use ° to save one-byte (the newline from using the command Radian)
:Radian :sin(X) can be :sin(X^^r)
- ° (degree symbol)